1. Field of Invention
The present invention relates to apparatus for winding elongated material onto drums and, more particularly, to portable apparatus for winding pilot lines upon drums to facilitate the handling of pulling lines or the like used in the stringing of power transmission conductors.
2. Technical Considerations
Power transmission conductors are generally suspended from support towers spaced along a path or route spanning vast sections of land. The conductors are often very large in diameter and therefore relatively heavy and cumbersome to handle. When the conductors are strung along their transmission paths, relatively large pulling forces are required to draw them off of their reels and over their support towers. To facilitate this effort, a socalled pulling line is first strung over the transmission path, and then the end of the pulling line is attached to the leading end of the transmission conductor and pulled back across the transmission path by a heavy pulling machine to string the transmission conductor.
As mentioned above, the transmission conductors are relatively heavy and therefore the pulling lines used for stringing them must be suitably strong. Pulling lines are generally steel cables, usually heavy and cumbersome to handle and, therefore, the pulling lines are strung by a relatively lighter pilot lines which are less cumbersome to handle. Each pilot line is generally made of strong, flexible, lightweight dielectric material such as polypropylene, and its flexibility provides easier handling in threading it through the blocks of the individual support towers to serve as a lead line in defining the ultimate transmission conductor path.
When a pilot line is positioned along the transmission path, its end is attached to the leading end of the pulling line for drawing the pulling line into place. Apparatus for handling pilot lines and stringing pulling lines must be capable of delivering pulling forces of many thousand pounds because of the size of the pulling line. Conventional apparatus has included a plurality of reels arranged side by side in coaxial relationship with a level wind means positioned before each reel. Such reels having individual clutch and brake mechanisms are usually rotated by a common drive shaft. Such a reeling arrangement has operational shortcomings in that as the pilot line is tightened by the reel rotation, it stretches, resulting in a reduction of the line diameter. The reduced diameter increases the force in pounds per square inch of the line upon the reel. The increase in force applied if often sufficient to severely damage underlying convolutions of line and to crush the reel.
Some of the prior art constructions have attempted to eliminate the crushing problem inherent in the stretching of lines by utilizing a bull wheel winder system. In such cases, the bull wheel system interposes the necessary reeling tension, accommodates the stretching of the line and supplies it at relatively light tension to the take-up elements. Generally in such constructions, a single bull wheel system is utilized in conjunction with a separate level wind apparatus for each drum. Level wind equipment is common in the prior art and generally comprises apparatus for guiding elongated material onto a spool or drum driven in rotation to reel in the elongated material.
In one prior art construction, the bull wheels are fixed in a position above a plurality of rotatably mounted drums arranged one behind the other with their axes in spaced, parallel alignment. The pilot lines are pulled in by the bull wheels and guided onto each reel by the individual level winds. Such an arrangement has operational and structural shortcomings, in that individual level wind apparatus is necessary and interference between pilot lines of adjacent reels is frequent. Also, since the bull wheel system must be positioned above the drums, an overturning moment on the apparatus is produced during the pulling of the lines and becomes a limiting factor in the operation.
Inherent in population growth is the expansion of cities and towns and the increased requirement for electricity. The need has thus been fostered for more efficient and powerful apparatus for facilitating the stringing of power transmission conductors. Such apparatus primarily must be mobile and compact to facilitate transportation with emphasis on safety, efficiency and economy in the stringing operation.